The instant invention teaches a system and method of extracting and conveying gases for sampling.
Any confined space in an industrial setting presents an insidious hazard to workers. A confined space is a defined volume that has limited openings for entry and exit and unfavorable natural ventilation. Such confined spaces may contain dangerous air contaminants such as toxic or inert environmental gases that will poison or suffocate an exposed worker. Examples of confined spaces in industrial settings include but are not limited to storage tanks, compartments of ships, process vessels, pits, silos, vats, wells, sewers, digesters, degreasers, reaction vessels, boilers, ventilation and exhaust ducts, tunnels, underground utility vaults, and pipelines.
The failure to recognize and control the hazards associated with confined spaces quite often results in injury or fatality to those who rush to the aid of workers exposed to such environments. Without knowledge of the composition of the environment, would-be rescuers are themselves at risk for injury. Generally, these environmental gases are invisible or barely visible as vapors; rescuers have nothing to warn them of the danger.
Normal atmosphere is composed of approximately 21% oxygen, 78% nitrogen, and 1% argon, with small amounts of various other gases. Individuals begin to suffer oxygen deprivation, or hypoxia, when the oxygen level drops below 17%. The first sign of hypoxia is a deterioration of night vision, generally not noticed by the victim. When oxygen levels fall to between 14% and 16%, physiologic effects include increased breathing volume, accelerated heartbeat, poor muscular coordination, rapid fatigue, and intermittent respiration. When oxygen levels fall to between 6% and 10%, the effects on a victim are nausea, vomiting, inability to perform, and unconsciousness. At concentrations less than 6%, the result is rapid loss of consciousness and death in minutes.
Any number of regular industrial processes can serve to foul the atmosphere by consuming oxygen. Welding, cutting, or brazing each consumes oxygen. Bacterias found in swamps and landfills and yeasts present in baking consume oxygen. Even a slow chemical reaction such as the rusting of exposed surfaces of metal tanks, vats, and ship holds consume oxygen.
Displacement of oxygen by inert gases can be equally fatal. Any gas with a different mass per volume than oxygen will displace the oxygen in the environment. Carbon dioxide, propane, argon, and helium, none of them toxic, will asphyxiate a worker by displacing necessary oxygen.
Where a fuel is present in the atmosphere, as results from the vaporization of flammable liquids, as by-products of chemical reaction, in enriched oxygen atmospheres, or in concentrations of combustible dusts, the presence rather than the absence of oxygen presents the principal hazard. Fuel and oxygen in the proper atmospheric mixture will combust explosively in the presence of a source of ignition. Any ignition source will doxe2x80x94a spark from a motor or the flame of a welding torch. A typical industrial setting is rich with ignition sources.
The proper or stoichiometric proportion of oxygen to gas for combustion will vary from gas to gas. The inherent properties of a gas fix a range defined as the lower flammability limit (LFL) and upper flammability limit (UFL) or lower explosive limit (LEL) and upper explosive limit (UEL), respectively. The explosive range for methane is, for example, between 5% and 15% in air. Concentrations below 5% methane are below the explosive range, and concentrations above 15% are too rich to support combustion. Where a confined space contains methane in, for example, a 27% concentration, the introduction of air will dilute the methane, making the formerly inert atmosphere explosive.
Firefighters responding to an industrial fire present themselves to far greater danger than might exist absent the fire. The heat of a fire vaporizes otherwise stable solvents, efficiently distributing flammable and likely toxic gases into the environment. Fire also removes oxygen from the atmosphere, thus dynamically shifting ratios of oxygen to fuel in the environment, possibly through the explosive range. By-products of combustion may themselves be toxic, or simply heavy enough to displace the oxygen in the environment.
Should the industrial fire be aboard a commercial vessel, the presence of a far greater number of confined spaces than might be present in a land-based industrial setting multiplies the dangers inherent in an industrial fire. Because the hull of a ship is not a strictly rectilinear form, the hull""s function compromises the shape of industrial workspaces aboard. The industrial functions aboard a vessel requires further compromises in hull design, resulting in tortuous passageways, multiple distinct and confined compartments, and a funnel-shaped skin of the hull, well-suited to directing heavy gases to the bowels of the ship.
In light of the many compartments susceptible to the collection of asphyxiating, flammable, or toxic gases in industrial and shipboard settings, whether during a fire or in the course of day-to-day operation, it is important to be able to sample gases within any confined space prior to entry. The Occupational Safety and Health Administration requires such sampling in regulation D94-01-048 entitled, xe2x80x9cSampling for Confined Space Entry.xe2x80x9d 29 CFR 1910.146(c)(5)(ii)(C). While such regulation does not bind firefighters and other emergency rescue workers (29 CFR 1910.146(k)), the potential for hazard and thus the need for sampling in this context is even greater.
Traditional gas sampling in industrial settings typically involves handheld devices including a blower, a short plenum, and chamber for sampling. One such sampling device, the LeakAlert(trademark), has, for instance, a 20-inch probe. This device conducts a sample of ambient air through the probe, exhausting the same at the far end of the chamber. Using this type of handheld device to detect ambient gases requires that the operator be within the environment tested. Moreover, using the same device to test air within a closed compartment, from the outside, acts to introduce the suspect gases into the operator""s own environment. Where the suspect gases turn out to be a fuel, this introduction may bring the level of gases in the ambient environment to explosive levels.
Yet another disadvantage with the prior art handheld devices relates to how potentially hazardous gases are ported to the ambient atmosphere from the system after testing. Traditional systems have used an aspirator bulb to draw a gaseous sample into contact with the atmospheric tester. Hand-operated aspirator bulb equipment therefore requires much effort to purge a lengthy hose and draw a proper sample from a confined space.
In light of the noted hazards and the above-identified disadvantages with the existing systems, important criteria emerge as necessary for the safe operation of a gas sampling system. First, a safe apparatus for gas sampling should be capable of exhausting the sample a safe distance from the operator or operators and should do so in an environment where the exhausted sample will readily dissipate. Second, the gas sampling apparatus must remove any ignition source from contact with the drawn sample; electric motors and compressors should be isolated from the gas-sampling stream. Third, the intake port for the apparatus must be portable to assure that sampling will take place at each level that workers will enter. A ponderous apparatus would prevent use in the tortuous passageways common in industrial settings. Good confined space sampling equipment comes with probes that operators can lower into the space.
The present invention comprises a system and method for extracting and conveying sampling gases from a remote location for component and quality testing by a gas-sampling device by use of a venturi-based manifold that moves a volume of motivating gases to create a venturi effect. The system includes an air extractor for creating a vacuum to draw sampling gases for testing. The air extractor includes a venturi having an inlet end and an outlet end, the inlet end further connected to a venturi jet through which the volume of motivating gas is drawn to create a venturi effect and the outlet end further connected to a horn through which motivating gases are vented to the atmosphere, an inlet port having a means for selectively interrupting the flow of motivating gases through the inlet port into the plenum, and a plenum extending from the inlet port to the inlet end of the venturi. The system includes a sampling manifold for testing the sampling gases drawn by the air extractor. The sampling manifold includes a housing defining a chamber in which the plenum of the air extractor is located, at least one manifold port through which the sampling gases from the remote location are drawn into the housing by the venturi effect created by the air extractor, the manifold port having a means for selectively interrupting the flow of sampling gases through the manifold port into the manifold, and at least one sampling port through which a sample of the sampling gases drawn by the air extractor into the housing of the manifold are drawn by the gas-sampling device, the sampling port having a means for selectively controlling the sample of sampling gases from the manifold to the gas-sampling device.
In an alternative embodiment, the system further includes a pressure gauge for monitoring and reporting the pressure of the gases within the manifold.
In alternative embodiments, the system further includes a temperature gauge for monitoring and reporting the temperature of the gases within the manifold.
In an alternative embodiment, the air extractor further includes a regulator assembly used to control the operation of the venturi. The regulator assembly includes a needle piston movably positioned with respect to the venturi that is used to control the volume of motivating gas that flows through the venturi and a regulator spring connected to the needle piston for adjusting the needle piston with respect to the venturi to optimize the flow of motivating gas and create the greatest vacuum with the least expenditure of motivating gas.
In an alternative embodiment, the sampling manifold includes an adjustable manifold plate between the manifold and the manifold port, the manifold plate having a hole that can be aligned between the manifold and the manifold port to allow flow of sampling gases from the manifold port into the manifold.
The method of the present invention includes the following steps: feeding high-pressure motivating gases through a venturi to create a venturi effect; extracting and conveying sampling gases from a remote location by use of the venturi effect created by the venturi; drawing sampling gases into a manifold through a manifold port; testing samples of the sampling gases from the manifold using the gas-sampling device; and venting the sampling gases from the manifold.
In an alternative embodiment, the sampling gases are extracted and conveyed from a remote location into the manifold via a manifold port, and the step of extracting and conveying sampling gases from a remote location by use of the venturi effect created by the venturi further includes selectively interrupting the flow of sampling gases through the manifold port into the manifold using a manifold port valve.
In an alternative embodiment, the step of feeding high-pressure motivating gases through a venturi to create a venturi effect further includes controlling the operation of the venturi by positioning a needle piston movably with respect to the venturi to control the volume of motivating gas that flows through the venturi and create the greatest vacuum with the least expenditure of motivating gas.
Alternative embodiments of the present method further includes monitoring and reporting the pressure and temperature of the gases within the manifold by use of pressure and temperature gauges, respectively.